Motor-control system



June 1, 1 926. a

- P. w. FQRSBERG MOTOR CONTROL SYSTEM Filed Jan. 30, 1926 3 Sheets-Sheet 1 h I j lnventor I Peter W Forsber g, y

His Attorney.

- P. W. FORSBERG MOTOR CONTROL SYSTEM Filed J m. 30, 1926 3 Sheets.5heet 2 Fig. 2.

SERIES MOTORING MAIN HANDLE lfiVentor 1 Peter W Forsberg y His A torney.

Patented June 1, 1926 lll ll l 'fifi fi l rh l hl PETER W. FGBSBERG, OF SCHENECTADY, N'E'r'a'l' YGRH, ASSEGNGR TO GENERAL ELECTRIC COMPANY, A GOB'EORATIOH OF NEW YORK.

MOTOR-CONTROL SYSTEM.

Application filed January 30, 1928.

My invention relates to the control of electric motors, particularly those employed in service wherein the imotors operate to i drive the load and also operate as generators to brake the load regeneratively when driven thereby.

The present invention is particularly advantageous in controlling the several driving motors of an electric locomotive or the like where a portion of the motors is en pioyed to furnish exciting current to the remaining motors during regenerative braking operation of the locomotive, as is de scribed and laimcd in my Patent No. 1,421,931, although the present invention is not necessarily limited to such an arrangement.

in the control arran 'ement of my. prior patent a plurality or manually operable controllers is ei'nployed in establishing the various motoring and regenerative braking connections of the motors, and the main controller is moved through the same SllCCQS". sive-operative positi ns during both braltin and motoring operation, in order to control the same regulating resistors which are utilized in both operations.

Hy present invention provides improvement which enable certain of the regulating resistors to be controlled by the main controller only during motoring operation w. lie the control thereof is transferred to an independently operable controller during regenerative braking; operation. In this way a more flexible and co venient control of the locomotive is obtained during regenr-rative l raking operation. This is particularly advantageous when service conditions it uire initiating regenerative braking of the locomotive at the lowest possible speed.

In carrying the invention into effectin preferred "form or locomotive control system, the interconnection of the driving motors in the various operating relations, such as series and parallel, during motoring operation, is controlled by a main controller which also varies the regulating resistors in circuit with the motor in order to vary the operating speed thereof. The interconnection-t the motors in the regenerative brak- 0 relation is under the joint control of the main controller and a selective controller,

and the main controller is arranged to (1011-.

trol only the resistors employed in regulating the excitation of the motors during recrial No. 85,007.

generative braking operation, while the independently operable selective controller is arranged to control the resistors which are connectedin the regenerative braking circuit of the motors. Thus, after the motors are connected in the regenerative braking relation the main controller may be operated to equalize theregenerated voltage of the motors with the line voltage and the selec tive controller then may be operated to remove the current limiting resistors from the regenerative circuit to permit subsequent control of the regenerated voltage and consequently the regenerative braking effect by the main controller.

The invention will be better understood fronra consideraion or the accompanying wings, in wl ich Fig. 1 is a circuit dia- "n s hemati *ally showing the main mond regenerative braking circuits of 7 ric locomotive, together with the regulating resistors and controlling switch mechanism employed therein; Fig. 2 is a chart showing the sequence in which, the various switches indicated in Fig. 1 are operated during both motoring and regenerative braking operation; Fig 3 is a circuit diagram showing the manually operable controllers, as well as the circuits controlled thereby for effecting operation of the motor controlling switch mechanism in the proper sequence and Fig. i is schematic diagran'i of the regenerative brat-Zing circuit connections.

As shown in Fig. 1,the locomotive driving motors 1, 2, 3, 5 and {6, are of the r ct cur cit series type having field windg 1, F F F and ll, respectivearran ed to receive power from ey T, through the overload circuit C. ll ir ful i l series relation, as well "ra-llel grouos 01'? three motors each, iotoring operation, with the resistors 1t le in circuit with the motors to regulate the operating speed thereon. For re-- lit) generative braking operation the motors 1, 53,42, and 6, are connected in series rela tion and'the motor 8 is connected to overexcite the several field windings thereof in the manner described and claimed in my prior Patent No. 1,421,931, although the ino tors may be over-excited in any other suit able way if desired.

The interconnection of the motors in the several operating relations and the control tit o! the regulating resistors R R are cfl'cctcd by the various switches illustrated grmninatically in Fig. 1. some of which, 153 shown. are of the well known electro magnetically operated contactor type, while others are shown as cam operated contactors. The cam operated contactors' are arranged to be actuated by a set of cams which are operated by an electrically controlled meumatic engine in accordance with the usual practice, and these contactors constitute a transfer switch having a series and a parallel motoring position and also a braking position as indicated in Fig. 3. The operating cams T. S. and the electromagnetic controlling valves SB and BS of the transfer switch also are indicated in Fig. 3. I

The reversing of the motor field connections as indicated by the dash lines in. Fig. l is accomplished by a suitable reversing switch which preferably is of the usual electrically controlled pneumatically operated type, although this switch has been omitted from the drawing to avoid complication thereof. V

The operation of the various motorv and resistance controlling switches indicated in Fig. 1 is under the control of the manually operable main-controller M. (3., the selective controller S. (l, and the reversing controller 6., of which developments of the contact segments are shown in Fig. 3. In general, the main controller M. C. is arranged to operate the transfer switch T. S. and the electromagnetic contactors 9 to 36 to control the interconnection, as well as the speed, of the motors in both the series and parallel motoring relations. The reversing controller R. C. determines the direction of operation. while the selective controller S. C. cooperates with the main controller to effect reduced field motoring operation and also regenerative braking operation of the motors and, in accordance with the present invention. is arranged to separately control the operation of a portion of the resistance control contactors during braking operation of the motors. The precise manner in which the controllers effect operation of the various switches best may be understood from the following description of the operation of the control system.

In the first place, it may he noted that the electromagnetic control valve BS is arranged to admit pressure to the pneumatic engine of the transfer switch when the operating winding thereof is deenergiised.

lillS insures that the transfer switch is operated from either the braking position B or the parallel position P to the series motoring position S when the manually operable controllers M. C. and S. C. occupy their respective off and full field positions in which they are shown.

ler lil. C. then noted. into the lirst operathe position. "It .th the controller (J. in J l the forward position l this csta lishcs an energizing circuit for the closing co of the line circuit breaker G. i). from the control supply source the segments 60 and of the main con ler, the single segment (52 of the controller, the segments 63 and (5-1 of so tact (35, thence through segn'ients (it; and t? of the main controller. to ground. The circuit breaker immediately closes and is held closed when the contact (35 opens under the control of the tripping coil 'l. C. in the main motor circuit and the holding coil (7.. which is energized from the source through the contact 38 of the rovers-hug controller. At the same time. the em gizim; circuit for operating wim s of :lectrw i'nagnetic contactors 19, 20. n 3.. and El is completed through the con terlocking segment of ti Since the cam contactors l2}, l6, and are closed with the traa. in position S, the driving motors nected to receive current from the tro through the resistors and it reversing controller, the winding G. O, con

lcy L the motors connected in full series oie atin l l l i the man re operating positions 2 to 14; serves to establish energ ing circuits for the electroma relation. The advancement of controller through the succcssi gnctic resistance controlling contactors in the sequence indicated in Fig. 2, and thereby grauualh: removes the resistances R and it from the motor circuit.

In the sequence chart shown in l will be observed that the resistance centre ling cont ctors 2T, 28, 30. 25. Ellil 1. closed successively as the main crmtrollcr M. C. passes throngl. positions 2. 3, 5 and (5, and in the control diagran'i in Fig. 3 1i w ll be seen that the oner 51112 circuits the operating windings or these extend through the auxiliary into!" segments 74:, '75, T6, 7'? and 78 v of the transfer switch. This gro p of resistance contactors is energized thr igh the transfer switch segments only when the transfer sw'tch is in the series or the 1 llel position. In the braking position of the transfer switch the control of this group of contactors transferred to the selectire con troller S. 0., as will be more fully pointed out hereinafter.

To operate the meters at a higher speed in the full series operating relation (in lective controller S. C. m g be moved from the full field running position in which shown into one of the reducediield positions RB, R in the first of which the elect-r0- magnetic contactors 33 and 3a are closed to shunt the motor field winning through the resistors R and 3* and the inductive shunts S and S respectively, and in the second of which the ccntactors 35 and 36 are closed to shortfcircuit these resistors,thereby leaving only the shunts S and S in parallel with the field windings.

If service conditions warrant operation of the locomotive at a higher speed, the selective controller S. C. is returned to the full field position F. F. and the main control ler is advanced into the first parallel position 15. In this position of the main controller both of the electromagnetic valve windings SB and B-S are energized in parallel circuit from the supply source through the segment 1, the circuitof the latter extending through the interlocking segment 72 of the transfer switch and the common return of the two windings extending through the contact of the circuit breaker in its upper position and the segments 73, and 67 of the main controller to ground. This results in the valve, SB admitting air to the pneumatic engine to move the transfer switch towards the braking position, whilethe valve BS releases the pressure tending to maintain the tansfer switch in the series position. In this way, the transfer switch is operated from position S. As po sition P is approached, the energizing circuit of valve winding BS is interrupted at the segment 72 and the valve functions to admit pressure to stop the transfer switch in position .1.

As the transfer switch is thrown from position S to P the cam contactors are 0p erated to change the motor connections from the series to the parallel relation, as indicat ed in the transition steps T T T of Fig. 2. Further advancement of the main controller through positions 16 to 24 serves to remove the resistors E a from the motor circuit in the sequence indicated in the parallel motoring portion of the chart shown in Fig. 2. Likewise, the reduced field operation of the motors in the parallel relation is ef fected by operation of the selective controller into either t is reduced field positions Bi or RF? lVhen it is desired to initiate regenerati've braking operation of the motors, the main controller MC is returned to the off position, thereby operating the transfer switch to interconnect the motors in the full series relation, if not already therein. The selective controller S. C. then is advanced into the first braking position B This establishes energizing circuits for hoth of the electromagnetic valves SB and BS, extending from the supply source through the segments 60, 61, of the main controller,

segment 62 of the selective controller, and thence through the valve operating windings in parallel circuit, the contact 65in its upper position and segments 73 and 67 of the main controller to ground. The valve SB admits air to the transfer switch operating engine to move the switch from the series to the braking position and the valve BS is maintained energized to release the air pres suretending to hold the braking switch in the series position. e

As the transfer switch operates to the braking position the motor cont-rolling cam contactors 41, 4-2, 14, 45, 47, 50, 51, 54 are closed and the electromagnetic contactors 18, 19, 20, 22, 23, 24-, 25, 27, 28, 30 and 31 are operated to connect the armatures of motors 1, 2, t, 5,6, in series relation through the resistor R and also R to return braking current to the trolley T. At the same time the motor 3 is connected in a closed circuit including the fields F F F F, F, F, with the resistor R together with the resistors R R and R connect-ed in the circuit in the manner described in my prior patent and illustrated in Fig. 1.

\Vith the transfer switch in the braking position, the control of the resistor is removed from the main controller M. C. and transferred to the selective controller S. C. The resistor R however, remains under the full control of the main controller M. C. Thus, with the resistor R in themotor circuit to limit the exchange of current between the motors and the trolley T, the main controller M. C. .may be operated to vary the exciting current supplied to the lield windings of the motors so as to bring the voltage generated by the motors 1, 2, 4, 5, 6, to a valuesuhstantially equal to or slightly in excess of that of the trolley 1, even when the motors are operating at very low The selective controller then is acvanced through the braking positions, 1, 2, 3, e1, :3, to successively operate the electromagnetic switches 27, 28, 30, 25, and there gradu ally remove the resistor R from the ln'alring circuit.

To increase the regenerative braking effect of the motors to the desired value. the main controller M. C. then is advanced to oper ate the electromagnetic resistance controlling contactors 7 to 17 in the sequence indicated in the regenerative braking portion of the chart shown in Fig. 2. This varies the point of connection of the resistor R to the resistor R and increases the over-excitation of the motor field windings thus causing the regenerated voltage and current of the latter to increase correspondingly.

As is fully pointed out and claimed in my prior Patent, No. 1,421,931, the braking current of the motors is regulated automatically to prevent a surge of current in case the potential, ofthe trolley T should iso suddenly decrease for any reason. Briefly, for interconnecting the motors in the brakthis is due to the tact that the resistor it lng relation with one portion of the said is so proportioned that the drop of potential across this i sistor upon an incipient increase in the braking current automatically de creases the excitation of the eliciter field winding F, and thus in turn reduces the exciting current supplied by the motor Since the resistance R in the regenerative braking circuit can be removed by operating the selective controller independently of the main controller, the regenerative volt age of the motors may be varied between wide limits by varying the excitation of the motor lield windings through operation of the master controller M. 0. without causing an excessive exchange or current between the motors and the supply lines. This is a di tinct advantage when it is desired to initiate regenerative braking operation at the lower-at possible speed 01' the motors.

What I claim as new and desire to secure by Letters Patent oi the United States, is,-

l. 'lhe combination with a plurality of electric motors and a plurality ol regulating resistors therefor, of switch mechanism for interconnecting tnc motors with said resistors in circuit therewith for both motoring and regenerative bralnng operation, means for controlling the said resistors and the said switch mechanism during 1110-- toring operation, and independently operable means cooperating with said lirst means to jointly control the said switch mechanism, and for separately controlling a portion of said resistors during regenerative braking operation of the motors.

2. The combination with a plurality of electric motors adapted for motoring and regenerative braking operation, of a plurality or regulating resistors "tor the motors, a controller having a plurality of operating positions for interconnecting the motors with said resistors i'or motoring operation and for controlling said resistors to vary the operating speed of the motors, and an in dependently operable controller arranged to cooperate with said first controller to interconnect the motors in the braking relation with said resistors in circuit therewith and for separately controlling a portion of the said resistors to vary the braking current of the motors.

3. The combination with a plurality of electric motors adapted for motoring operation and for regenerative braking operation with a portion of the motors operating as ezzciters tor the other motors, or a plu rality oi regulating resistors, a controller for interconnecting the motors for motoring operation and for controlling the said resistors to vary the operating speed 01" the motors, and an independently operable controller cooperating with said first controller resistors in the braking circuit and another portion of the resistors in the excitation circuit, said independentl operable controller being arranged to separately control the portion of the resistors in the braking circuit.

4 raw fr.- ihe combination with a plurality oi? electric motors and a plurality of regulating res stors therefor, ot' switch mechanism for interconnecting said motors in series and parallel relation for motoring operation with said resistors in the motor circuit and for connecting a portion of the motors to overexcite the remaining motors witn one portion of said resistors in the braking circuit and another portion of the resistors in the esfitation circuit for regenerative braking operation, a con roller having a plurality o operative positions for controlling said rcsi, oi-s during motoring operation and for controlling the said portion of the resistors in the excitation circuit during braking operation, and an independently operable controller arranged to separately control the portion o l the resistors in the l'n'alzing circuit.

5. in a control system for a plurality of electric motors adapted for motoring operation and for regenerative braking operation with a portion of the motors acting as excitlor the other motors, the combination of a plurality of resistors, switch mechanism "or connecting said resistors in the motor cult during motoring operation and for "ontrolling the resistors to vary the operating speed 01 the motors, and independently le switch mechanism cooperating with said first switch mechanism to connect one portion of said resistors in the motor circuit and another portion of said resistors in the excitation circuit of the motors tor regenerative braking operation and for separately cam-trolling the portion of the resiz'itors in the motor circuit to control the braki g current of the motors.

are combii'iation with a plurality of direct cur nt series motors and a plurality of regulating resistors thcretor, oi switch i'hechanism for connecting the resistors in series with the motors for motoring operation and for connectiiur one portion of the resistors in series with one portion of the armatures ot the motors to :torm a braking circuit and another portion of the resistors in series with the other portion oi the armatures and the hold windings of the motors to term an excitation circuit, a controller having a plurality of operative positions for controlling said resistors to vary the speed of the n'iotors during motoring operation and for controlling the portion of said resistors in the excitation circuit during braking operation, and a separately operable controller having a plurality of operative posilllt) tions for separately controlling the portion of said resistors in the braking circuit.

7. The combination with a plurality of direct current series motors and a plurality of regulating resistors therefor, of electroresponsive switch mechanism for connecting; the motors in series and in parallel relation with said resistors in circuit therewith for motoring operation and for interconnecting a portion of the motors to excite the remaining; motors with one portion of said resistors in the brakin circuit and another portion of the resistors in the excitation circuit for regenerative braking operation, a pair of separately operable controllers each having a plurality of operative positions, and connections through which one of the controllers controls the operation of said electroresponsive switch mechanism during motoring operation and said controllers control said electroresponsive switch mechanism during regenerative braking operation with one of the controllers separately controlling a cor responding portion of the resistors.

In witness whereof, I have hereunto set my hand this 13th day of January, 1926.

PETER W. nonsense. 

